Investigation of structural parameter dependence of confinement losses in PCF–FBG sensor for oil and gas sensing applications

Photonic crystal fibre (PCF)–fibre bragg grating (FBG) integration opens up new possibilities in multi-parameter fibre-optic sensing, owing to their active control over light characteristics and mode confinements. Their integration results in a mismatch in their mode field diameters (MFDs), which in turn causes various types of losses such as confinement loss, scattering loss, etc. This paper primarily investigates the effect of geometrical parameters on fibre parameters such as confinement loss and MFD, which plays a significant role in long distance fibre-optic remote sensing. Liquid crystal PCFs (LCPCFs) are utilized in the sensor configuration, exploiting their optical properties for photonic bandgap based tighter mode confinements and wavelength tunability. Furthermore, the LCPCF–FBG combo enables multi-parameter fibre-optic sensing which can be effectively utilized in oil and gas sensing applications. Theoretical study conducted on the fibre sensor revealed that confinement loss and MFD can be reduced by properly optimizing their structural parameters.